1. Field of the Invention
The present invention relates generally to a wireless remote access base station converting an optical signal to a radio frequency (RF) signal and utilizing the converted RF signal for wireless communication, and in particular, to a wireless remote access base station including an electro-absorption modulator (EAM).
2. Description of the Related Art
A method of transmitting an optical signal from a central office to a relay base station and transmitting a radio frequency (RF) signal from the relay base station to each subscriber is known as a radio-over-fiber (ROF) method. A system using the ROF method is called a pico-cell system, which includes a wireless remote access base station for transmitting/receiving data by converting an optical signal to an RF signal and an RF signal to an optical signal.
FIG. 1 is a configuration of a conventional ROF type pico-cell system 100 including a wireless remote access base station 130. As shown, the pico-cell system 100 includes a wireless router 110, an optical transceiver 120 for generating a downstream optical signal and receiving an upstream optical signal, and the wireless remote access base station 130. The pico-cell system 100 can transmit a downstream RF signal to a portable digital communication device 140, such as a personal computer (PC) 142 or a personal digital assistant (PDA) including a wireless local area network (WLAN) card 141, or convert an upstream RF signal received from the portable digital communication device 140 to an upstream optical signal. The optical transceiver 120 and the wireless remote access base station 130 are linked using a downstream optical fiber 101 and an upstream optical fiber 102.
The wireless remote access base station 130 includes an electro-absorption modulator (EAM) and an antenna. The antenna receives an upstream RF signal and transmits a downstream RF signal to the portable digital communication device 140 in a wireless manner. The EAM converts an upstream RF signal received via the antenna to an upstream optical signal and transmits the converted upstream optical signal to the optical transceiver 120. The EAM also converts a downstream optical signal to a downstream RF signal and transmits the converted downstream RF signal via the antenna in a wireless manner. The EAM can operate even without applying a separate bias voltage, thereby enabling a simple wireless remote access base station structure.
However, without applying a bias voltage, the sensing characteristic of an RF signal is low, and the service coverage is limited within an area of a 1 m radius.